This invention relates to a fluid displacement apparatus, and more particularly, to a scroll type fluid displacement apparatus with improved spiral elements.
Scroll type fluid displacement apparatus are well known in the prior art. For example, U.S. Pat. No. 801,182 issued to Creux discloses the basic construction of a scroll type fluid displacement apparatus which comprises a pair of scrolls each having a circular end plate and a spiroidal or involute spiral element. The scrolls are maintained angularly and radially offset so that both spiral elements interfit to form a plurality of line contacts between their spiral curved surfaces to thereby seal off and define at least one pair of fluid pockets. The relative orbital motion of the two scrolls shifts the line contacts along the spiral curved surfaces and, as a result, changes the volume of the fluid between the spiral elements. Thus, scroll type fluid displacement apparatus may be used to compress, expand or pump fluids.
Scroll type fluid displacement apparatus are suitable for use as refrigerant compressors. In scroll type refrigerant compressors, refrigerant gas generally is taken into fluid pockets formed at the outer most end portion of the spiral elements. The fluid pockets are gradually compressed as these fluid pockets are moved toward the center of the spiral elements due to the orbital motion of the orbiting scroll. Finally, when compressed fluid reaches the central portion of the interfitting spiral elements, the compressed fluid is discharged to an external fluid circuit. As a consequence of the above operation, the temperature and pressure of the refrigerant gas are maximized in the central portion of the interfitting spiral elements.
In prior art scroll type compressors, the spiral elements generally have a uniform thickness, i.e., the thickness of the spiral elements from the inner end portion to the outer end portion is the same. In the past, when the thickness of the spiral element, particularly the central portion of the spiral element, was increased to achieve sufficient mechanical strength, the thickness of the entire spiral element from the inner end portion to the outer end portion was likewise increased. As a result, the weight of the scrolls increased, and the centrifugal force generated by the orbital motion of the orbiting scroll increased. This increase in the centrifugal force of the orbiting scroll has caused several problems, such as excessive wearing of the scrolls and other damage to the scrolls and the scroll type refrigerant compressor.